The development of measurement techniques to determine the thermal properties has been a very active area in the last decades. Lately the existing methods which use scan calorimeters suffer some deficiencies. For instance, in some devices it is necessary to use small samples with a large surface—volume ratio; in unstable solutions this produces the loss of volatile components during the placement of the sample. The present designs don't allow the use of large samples because the sample heating is made through the container's heating. This requires that the time for temperature is homogeneous in the sample; this factor is highly dependant on the sample's size. In some calorimeters the container is larger than the sample, which might produce a mass exchange between the sample and the empty space in the container. When the volatile components evaporate into the container's empty space, aside of introducing heat measuring errors, the balance of the chemical reactions can be affected, for example, diminishing the water contents or catalytic components in the sample.
In the presently known calorimeters, where the heat generation is internal, this might be done due to different phenomena such as chemical reactions, light absorption, sound absorption, particle absorption and electrical dissipation. The inwardly generated heat quantification is usually made by measuring the heat changes in the container, in this way, the transferred heat from the sample to the container is an effect integrated during the measurement, and these calorimeters require of this heat transference to work.
Among the documents that define the state of the art already mentioned there is the U.S. Pat. No. 4,130,016 in which it was divulged an adiabatic calorimeter designed to the high risk chemical research, particularly in studying the auto-heating reactions which can give situations of little control, wherein the reaction's recipient and the associated components in this device simulate closely the structure and the operation of a typical plant chemical reactor, finally this patent describes that the reaction's container is placed inside a metal cover and the whole unit is suspended in an isolated oven.
Another state of the art document which describes a calorimeter in which the heat is produced by light absorption is the U.S. Pat. No. 4,185,497 that describes a device to measure the energy absorption by the measurement material, wherein the temperature of the container in which the sample suspended is controlled, such container is a vacuum vase or deposit, the document also describes that the calibration is made by a known dissipation rate of the sample's energy. The sample is irradiated by a light beacon of a known power and the increase of the temperature in the sample is compared with the corresponding temperature increasing of the calibration sample. A method to scan the sample's heating is also provided. Another document, U.S. Pat. No. 4,765,749 exposes a calorimeter in which the generated heat inside the sample is made by the Joule's effect, more particularly, a calorimeter to measure energy transported by radiation and that have an external side exposed to the radiation and an inner side, said element experiences an increase in temperature during the interaction with the radiation and this temperature raising is measured by a thermo battery. Finally, the U.S. Pat. No. 7,012,820 B2 exposes and protects a calorimeter that seeks to obtain adiabatic conditions, in which the transferred heat from the sample to the container is calculated and the heating system is adjusted during the system's operation to compensate this heat loss.
From the technical knowledge obtained by the analysis of the above mentioned documents we can state that presently there is no resistive calorimeter which, starting with a scan can determine the specific heat of samples such as plaster, humid minerals and some food systems and, besides that, such heat quantity measurement process is made under adiabatic conditions.
Based in the mentioned above, we defined the following: